1. Field of the Invention
The present invention relates to an underwater propulsion apparatus which is designed to generate an electromagnetic force by application of an electric field and a magnetic field in substantially perpendicular directions in water. More specifically, the present invention relates to an underwater propulsion apparatus to be mounted on a ship as a primary drive therefor. The present invention also relates to a method for propelling a ship by application of electric and magnetic fields that are substantially perpendicular.
2. Description of the Related Art
Since the 1950s, it has been considered to apply an electric field in a direction perpendicular to a strong magnetic field, so as to obtain an electromagnetic force which is used for propelling a submarine or ship, or for transferring a liquid.
Conventional propulsion methods are limited in propeller turning force, and cannot achieve sufficient speed. On the other hand, the above method using the electromagnetic force, in which the speed increases in proportion to the respective strengths of the electric field and the magnetic field, can obtain a sufficient high speed. However, the idea was not put to practical use in the 1950s when it was impossible to produce a strong enough electric field and magnetic field to obtain a desired high speed.
The recent practical superconducting magnet, capable of producing a magnetic field of the order of several teslas, is expected to make it practical to use the electromagnetic force for ship propulsion. In fact, this idea has proven successful experimentally. Presently, it is possible to produce a strong magnetic field by the aid of a superconducting magnet. However, the electric field must also be sufficiently strong in order to obtain a satisfactory high speed.
When the electric field is applied to water, water and materials dissolving in water are electrolyzed. That is, an electric current is sent so as to electrolyze water or seawater. The electrolysis produces hydrogen gas, oxygen gas, or the like. Although the electrolysis merely consumes a negligibly small portion of electric power, hydrogen gas and sodium hypochlorite are produced in case of seawater electrolysis. Hydrogen is explosive, in spite of its small amount and diffusibility into air. Sodium hypochlorite, which is an oxidizing agent and disinfectant used for water purification, may form organic chlorides which cause environmental pollution, although it would pose no toxicity problem after dilution.
Upon the electrolysis of seawater (i.e., the electrolysis of water including sodium chloride), chlorine ions and hydroxyl ions in seawater preforms either or both of the following reactions as the result of their oxidation (or loss of electrons) on the anode. EQU 2Cl.sup.- .fwdarw.Cl.sub.2 +2e.sup.- ( 1) EQU 4OH.sup.- .fwdarw.O.sub.2 +2H.sub.2 O (2)
Although it is possible to cause to proceed either of the other reactions by selection of an adequate electrode, usually the reaction (1) is caused to proceed predominantly and the produced chlorine gas reacts with sodium hydroxide obtained on the cathode to produce sodium hypochlorite according to the following reaction. EQU Cl.sub.2 +2NaOH.fwdarw.NaClO+NaCl+H.sub.2 O (3)
A manganese compound mainly including manganese dioxide is used for the seawater electrolysis so as to be able to cause reaction (2) to proceed selectively. Such a manganese compound is satisfactory for laboratory use. However, the compound does not have a long enough life because of slightly poor conductivity and chemical stability thereof under a high current density of 50-100 A/dm.sup.2. At present, there are no substance in its stead.
Even though it is possible to produce a substance which causes reaction (2) to proceed selectively without the environmental pollution, there still remains a serious problem in that the evolution of detonational oxyhydrogen gas is not only dangerous but also undesirable because it impedes the water flow and lowers the propulsive force. Accordingly, it is not preferable to diffuse the gas into air.
In order to avoid the gas production which is accompanied with the above problem, a gas electrode is used to depolarize with gas. For example, instead of the anode reaction represented by formula (2), there takes place a reaction as indicated in formula (4) below without evolving gas, if the anode is supplied with hydrogen continuously. In addition, instead of the above cathode reaction, there takes place a reaction as shown in formula (5) below without evolving gas, if the cathode is supplied with oxygen continuously. EQU 2OH.sup.- +H.sub.2 .fwdarw.2H.sub.2 O+2e.sup.31 ( 4) EQU 4H.sup.- +O.sub.2 +4e.sup.- .fwdarw.2H.sub.2 O (5)
In general, a gas electrode includes a hydrophilic layer and a hydrophobic layer. The hydrophilic layer is in contact with the electrolyte and gas for a reaction. However, when the catalyst in the hydrophilic layer contacts an electrolyte having impurities, especially seawater, it is easily tainted by the impurities. Although the gas electrode has satisfactory efficiency in the beginning of sending the current, the gas electrode becomes ineffective by poisoning the catalyst in a short time in its practical use, such as in seawater; therefore it cannot solve the above problem.
There is a further problem in that a gas supplied to the gas electrode through the hydrophobic layer has to be a high-purity gas under high pressure. Accordingly, such a problem limits the size of the electrode. For the reasons mentioned above, the gas electrode has never been put to practical use for the propulsion apparatus which uses electromagnetic force.